"Once a year, you do something that you’re really not sure you can do. There are just two rules: you have a fifty-per-cent chance of success at best, and it doesn't kill you.”
In other words, Misogi is a physical trial. A trial that should not be a trained, paid or promoted affair. In other words, no marathons or obstacle races.
On the opposite side of Misogi you have micro adventures. Little adventures you can do in a day or a (long) weekend. I always try to do a couple of those a year.